1. Field
A safety mechanism designed for an on-board hydrogen storage and supply system to deliver hydrogen to a vehicle powertrain is disclosed. The mechanism provides a safety warning and shutdown system and method for hydrogen storage devices.
2. Description of Related Art
Hydrogen is the most abundant element in the universe and can be a great energy source. Hydrogen is increasingly touted as the fuel of the future since hydrogen can yield significant environmental benefits and can be produced from a variety of fossil and renewable energy sources. Hydrogen can be stored in compressed or liquid form or in solid state either chemically or through adsorptive means.
There exist three fundamental requirements for a hydrogen storage system: (1) the ability to receive fuel from an external source; (2) provide enough fuel storage capacity to allow the powertrain to provide adequate travel range for the vehicle; and (3) supply fuel on demand, at the required rate, to the powertrain.
However, due to the low energy density of hydrogen, storage of the hydrogen is challenging. Currently, one way hydrogen may be stored is in high pressure containers. These containers must be large and are subject to stresses and strains during each pressurization cycle, leading to material fatigue and a reduction in strength.
Presently compressed hydrogen on-board storage systems are designed to support 750 to 1,000 fill cycles per year, for a period of about 15-20 years. The pressure vessels are tested to support 15,000 leak and rupture-free cycles and for an additional 30,000 rupture-free cycles. Assuming a range of 200 miles per fill, the current requirements equate to 150,000 to 200,000 miles per year, leading to considerable over-design and resulting in weight and cost penalties to the container design. As a result, current container designs are not cost effective.
In the absence of well-defined mechanisms to assure that systems that exceed cycle life are positively taken out of service, the industry continues to encourage over-design as the only means of assuring safety. This results in higher costs for production and maintenance of on-board hydrogen storage and supply systems.